The overall aim of this research is to understand how the circulatory system is controlled, with the ultimate objective of determining which control factors are most directly involved in the production of essential hypertension. This project will examine what role the higher (forebrain) levels of the nervous system play in adjusting the cardiovascular (CV) system's response to normal, everyday activities. Specifically, the research aims are to: 1) Acquire normative CV data (heart rate, arterial blood pressure, renal and femoral blood flows) from social groups of baboons in which equal numbers of males and females are studied. The relationships between the menstrual cycle and the CV responses will be assessed in the females of this group. 2) In these same groups, determine the changes. in the levels of blood borne cardioactive hormones during normal behavior. 3) Complete studies of the influence of the perifornical region of the hypothalamus on both the cardiovascular and the hormonal responses during behavior. 4) Determine the effects of removing those parts of the amygdala that project to the perifornical hypothalamus on the CV and hormonal responses during normal behavior. 5) Apply modern data acquisition, analysis and archival technology to make these data available to other investigators. Two individuals of a four member social baboon group will be equipped with telemetry devices. Measures of arterial blood pressure, heart rate and renal and femoral blood flows will be transmitted to a central recording station while simultaneously recording the ongoing, free ranging behavior of the group. Blood samples will be taken remotely and assessed for levels of catecholamines, angiotensin, vasopressin and cortisol. The behavior will be coded and categorized and then linked to the associated CV and hormonal changes by automated computer analysis. The normal CV responses and hormone levels accompanying different kinds of behavior will be determined and the effect of removing parts of the hypothalamus and amygdala on those responses will be determined. These studies will yield information on which behavior patterns lead to elevated blood pressure and will define the neural structures responsible for those elevations.